1. Technical Field
The technical field relates generally to motor vehicles and, more particularly, to power management of vehicle traction batteries for balancing their state of charge.
2. Description of the Technical Field
Hybrid electric vehicles typically use a high voltage, direct current (DC) electrical power storage architecture in which a plurality of high voltage DC storage devices/traction battery packs are arranged in series. The traction battery packs can be individually tapped and can be discharged at different rate/s than other traction battery packs in the series. Adding to this dynamic is the parallel support of at least one least one secondary electrical architecture (and its attendant loads) at a lower electrical voltage potential than any one traction battery pack. This situation becomes problematic when one or more of the high voltage DC storage device's voltage level/s (or more precisely state of charge which voltage level is a proxy for) deviates from others in the system by a specified amount. Depending on the level of variation in the state of charge between high voltage DC storage devices and the interval of time for which the variation is sustained, such voltage variances can result in reduced high voltage DC storage device life, performance and efficiency.
U.S. Pat. No. 6,275,004 relates to a operation of a battery pack for a hybrid-electric drive train. The system regulates the voltages and states of charge of battery modules in the battery pack to balance the charging and discharging of the individual modules. This serves to extend the cycle life of the battery pack.